The present invention relates to releases (latches) which are held closed by means of magnets and which open when the magnetic field is removed or altered, and more particularly to such a release capable of submergence in water and having a low electrical power requirement, and which when used in combination with a system for signalling the release to open, can release from anchorage instruments and equipment which must operate submerged in the ocean or in freshwater lakes and/or rivers.
Devices, instruments and equipment must frequently be anchored in the ocean or in freshwater at depths or in situations which make direct mechanical or electrical connection with the apparatus by operators, or manual tending of them difficult or impossible. Frequently it is desirable to recover these devices for re-use. A common technique for recovery has been to anchor them with a latch or lock mechanism which can automatically or remotely be triggered to release and use added buoyancy to float them to the water surface. A variety of mechanisms have been used for holding the latch firmly closed during anchorage and opening the latch when needed. These include devices which remove pins by the motion of worm gears and electrical solenoids; wires or links which corrode or dissolve in water and thereby open latches; and latches which open by means of explosives or pressurized gases.
The current invention is a latch mechanism which is held in a closed position by the force of magnetic attraction between a permanent magnet and a metal plate. The latch opens when the magnetic field holding the latch closed is weakened, through a technique which diverts the magnetic flux, and a spring overcomes the force of magnetic attraction and forces the latch open. In the invention, the permanent magnet is not in direct contact with the plate but rather its magnetic field is channelled to the plate through the combination of a piece of soft magnetic alloy material and a pair trapezoidal steel plates which focus the field. The soft magnetic alloy material that so channels the magnetic field to the plates, is U- or horseshoe-shaped, with the ends of the arms on the open part of the U corresponding to the location of the two focussing plates. The permanent magnet contacts the soft magnetic alloy U between and midway along the two arms of the U. When the plate from the latch mechanism makes contact with the trapezoidal metal pieces, the configuration of the magnetic latch components becomes a loop. This configuration encourages the establishment of a strong magnetic flux there.
A second magnetic circuit or loop contacting the permanent magnet also exists within the device. In this case it is formed by the combination of the closed part of the soft magnetic alloy U and the permanent magnet. The overall magnetic flux of the permanent magnet is balanced between the flux in each of the loops in the device. In the current invention the flux in the loop which holds the latch mechanism closed can be disrupted by subjecting that loop to an electromagnetic field created by directing an electric current through a wire coil placed around one of the arms of the soft magnetic alloy U. When this occurs most of the magnetic flux is diverted to the second soft magnetic alloy loop, and consequently weakens the flux in the main loop. The flux can be weakened to such an extent that a spring on a lever arm on which the metal plate on the mechanism is mounted, can pull the plate away from the metal focussing plates and open the latch. Control for the device comes from an electronic control sytem linked to an acoustic transducer. Upon detection of acoustic signals from a remote source, the controller turns on a flash circuit which briefly supplies an electrical current to the coil which surrounds one arm of the magnetic alloy U, thereby effecting the opening of the latch. A key feature of the device is that the magnetic field used to secure the latch mechanism in a closed position can pass through a pressure housing separating the magnet and soft magnetic alloy material from the trapezoidal metal focussing plates which contact the plate on the latch mechanism. This enables opening of the latch to be controlled without the need for mechanical components which pass through the pressure housing.
The objectives accomplished by this invention are: to provide a latch mechanism, for use submerged in the ocean or in freshwater, which remains tightly closed but can be opened automatically or remotely when used in combination with a system which controls the release by supplying an electrical current at the time of desired release; to provide a remote latch device which is simple, has few moving parts, low power consumption and is likely to be highly reliable; to provide an electronic means of opening a latch and therefore enabling precise control of the operation; to provide an automatic or remotely operating electronic catch mechanism which has no parts that penetrate into a pressure housing which separates the electronics from the water, and therefore requires no seals, removing all possibility of leakage.